Pulse discrimination system



p 1949- G. w. LENNY, JR., ETAL 2,482,782

PULSE DISCRIMINATION SYSTEM Filed Feb. 13, 1947 Y 2 Sheets-Sheet 1 I I2 r "'I IIIE'LJ; I I4\ If I g I GATED GATE PULSE GATE PULSE I [OK I AMPLIFIER GENERATOR GENERATOR TRANSMITTING I J I DEVICE '7 M I I L, PULSE J POWER 1 x I MIXER AMPLIFIER I- H RECEIVING AMPLIFI OUTPUT I DEVICE DEVICE DEVICE g l PULSE POWER I I MIXER ''AMPLIFIER"" I 16 I l PULSE AMPLIFIER GENERATOR Ii I l L I III-3'33 as A L I I I L INPUT TERMINALS 20 B ANODE 22 m r iI c ANooE 30 D a r -ANODE 39 7s 18 so GEORGE W. LENNY JR.

PAUL E. WARD flue/wag Sept. 27, 1949; -G. w. LEI-NY, JR., ET AL 7 2,482,782

PULSE DISCRIMINATION SYSTEM Filed Feb. 15, 1947 v 2 Sheets-$11691. 2

GEORGE W. LENNYJR. PAUL E. WARD Patented Sept. 27, 1949 i, UNITED :oE -Frc:E

' GeorgeWa-Lenny, In, and-Paul Ward, I

United States Naval Reserve Application Febru-ary 13, 1 947 Serial'-N0.'728,212

h ".3;Claims. (o1..250 27-') (Granted under the act of March 3, "I883,as

This invention relates to pulse discrimination systems and in particular to a system .forproducing vamplitude varying signals in dependency Lon repetitive multiple v pulse .signals applied thereto.

Frequentlyitiis desirable to pro'duce amplitude varying signals in responsev to recurrence ireiquency' modulated ulse-'type signals. Such a situationlwouldlaris lin 'the case of asignaling system employing repetitive pulsed energy with variation in .the time Jspacing between selected pulses to convey in'telligence. Typical of such .a system is a transmitting and receiving system in which intelligence is applied -.'to repetitive ,pulse vpairs by selective variation o'fthe ,pulseiinterval between theindividual pulses of the pairs of pulses. To reproduce .thetransinitted intelligence in the form .of intelligible signals, a decoder or Kdiscriminationsy'stem must be employed in conjunction with the receivingcsy'stem.

Accordingly it is air-object of this invention to provide a systemior producingamplitude varying signals in response to repetitive multiple pulse signals having selectable pulse intervals. r Another object ;is to provide .a discrimination system responsive -to repetitive pairs of pulses .to produce amplitude varying signals in dependency thereon. a I e 1 A viurtheroloj ec't is to provide .a discrimination systemfor producing signals having amplitudes and polarity'independency on repetitive multiple pulses having variable pulse intervals applied thereto. 1 1

--Other and iurther objects and v-ieatures of the ,present invention will become apparent upon :a careful consideration lot the ,iollowing detailed descriptionwhen taken (together with the accompanying drawings which illustrate a typical embodiment of the invention and the manner in which that embodiment may he considered to operate. 7 w

i .Fig. 1 isa block diagramshowing'the general features of the present invention as employed in combination withtransmitting vand receiving devices.

,.Fig. 2 is a schematic diagram .of a specific circuit designedcto perform functions as hereinbefore outlined, i

Fig. 3 shows waveforms-taken to illustrate the operation of the circuit pf Fig. .2.

With reference to Fig. ,1 a .systemis shown which is representative Lof one embodiment of the invention andrwhich is adapted to operate on a group of repetitive'pulsesjin suc'ha manner that multiple'pulse signals may Ib'e'utilize'd to produce an amplitude varying 'signalfinidependency Ion amended April so, 1928'; 370 0. 37

time spacing characteristics of the multiple ls j 'Atransrnitting devicefll represents any energy sourceipreferahly adapted to produce apa'ir of radiofrequency pulses having selectallr'ile time spacing at a given repetitive irequency. Apart of the energy produced transmitting device I I) 'is radiated .outwardand intercepted "by receiving jdevice ii. .Ziny conventional ,r'eceiver'adapted to ipuise energy'reception may be employed in receiving device H iThe' intercepted energy is applied to the discrimination'isystem 12 after being amplified in a conventional amplification device "1'3.

A'first'pulse of a pair of receivedjenergy pulses triggers 'a 'first gatepulse generator I24 which subsequently causes operation of a second gate pulse generator The secoiidjpiilse of the pair of received energy pulses causes operation of a con- ,trol pulse generator .I 6 reproduce falpa'ir of polar- 'itjy opposed control signals; The output signal of thjefirstggate pulse get1 "e'raftor M is combined with a first one of the polarity opposed control signals jIr'om control pulsesgenerator 1T6 in a pulse mixer .17. t

;' Similarlygthehutfifit signal of the second gate pulsegeneratorflj'd 'is combined with the second off the polarity opposed control signals from control pulse generator Hi inpul'se mixer I18.

An output device l3 iiperatively connected .to pulse mixer 11 and L8 utilizes the outputs there- "from in such a'manner-as to produce amplitude varying signals in dependency upon "the phase characteristics iii/the pair or pulses intercepted by "receiving device H.

."I n particular, the pulse discrimination system files "typified 'by the exampleshown in Fig. '2 ineludes "input terminals '20 to which are applied repetitive multiple ,pulse signals intercepted by receiving device .l'l. Theseimultjiple pulse signals as hereinbefore mentioned preferably comprise a pair of pulses having selectable "time spacing. Thefintercepted pulses "having been (amplified in amplification device I 3 appear at "input terminals 20 .as positive pulses of energy.

' Application or a lpair pfpos'itive pulses to a control grid electrode .or amplifier 2] results in negative voltage -at anode 22 of amplifier 2i; Negejtii' e pulses formed .at the ,anode22 are applied toagrid1 3 of a resistancejc'agpacitance coupled amplifier 124 through V a coupling' capacitive elementl'25. Resistance-capacitancecoupled amplifier together withia second amplifier 26 make up a conventional one-shot 'rhultivibratoi 27 inWh'iEhffibeYl is normallyconductive because of the connection of grid 23 to the anode supply potential through grid resistive element 28. Application of a negative pulse to grid 23 alters this condition producing anode current flow in tube 26. This conductive condition of tube 26 is maintained until capacitive element 28 discharges sufiiciently to permit the grid 23 to rise above cutofii resulting in anode current flow in tube 24. Accordingly, impression of a negative pulse on grid 23* of tube 24 results' in the formation at the anode 30 of tube 24 of a positive pulse having a preselected duration. The duration of the output pulses formed at the anode 30 of tube 24 is substantially dependent uponthe values of capacitive element 29, grid resistive element 28, and the potential to which the grid 23 is connected through resistive element 28.

The anode 36 of tube 24 is operatively connected through a difierentiating network comprising resistive element 3| and capacitive elements 32 and 33 to a grid 34 of a resistance-capacitance coupled amplifier 35. Amplifier 35 is operatively connected to a similarly constructed amplifier 36 and forms a one-shot multivibrator 31 in which tube 35 is normally conductive. Multivibrator 31 is preferably similar in construction and thus operable in the same manner as multivibrator 21. .A positive pulse formed at the anode 30 of tube 24 and coupled through the differentiating network having elements 3|, 32, 33 appears at the grid 34 of tube 35 as first andjseriond voltage pips coincident respectively with the leading and trailing edges of the positive pulse formed at anode 30,

The anode 52 of tube 45 is connected through an impedance matching device 52A to a screen grid 53 of a coincidence tube 54. Impedance matching device 52A may be a conventional cathode follower network employed to prevent capacitive loading of trigger circuit 41 by grid 53 and associated leads. The anode of multivibrator 21 is coupled to the control grid 55 of coincidence tube 54. In the quiescent state before applying signals to coincidence tube 54, anode a current does not flow therein by reason of low the first voltage pip of a positivepolarity and the second voltag pip of a negative polarity. Only negative voltage excursions impressed on grid 34 will initiate regenerative switching action in multivibrator 31, therefore a positive pulse will be produced at anode 38 of tube immediately following the production of a positive pulse at anode 33 of tube'24. Circuit elements of multivibrator 31 are preferably selected so that positive pulses formed at anode 38 are of the same duration as pulses formed at anode 38 of tube.

24. It should be noted that voltage pulses will be formed at anode 39 of tube 26 and anode 40 of tube 36 coincidentrespectively with the formation of pulses at anode 36, and anode 38, the pulses formed at the corresponding anodes of either multivibrator being of opposite polarity.

Signals applied to input terminals 26 are coupled intoa conventional amplifier 4| as well as to amplifier 22. Anode 42 of tube 4| is coupled to grids 43 and 44 of tubes 45 and 46 respectively. Tubes 45 and 46 are operatively connected to form an Eccles-Jordan type trigger circuit 41. In the quiescent state before the application of pulses to trigger circuit 41, tube 46 is conducting current whereas tube 45 is maintained with anode current cutoff. Output from tube 4| in the form of negative voltage pulses applied simultaneously to grids 43 and 44 will have no direct effect on the non-conducting tube 45. However a negative voltage pulse of sufficient amplitude will cause the grid .44 of the conducting tube 46 to drop below cutoff. Regenerative switching action of trigger cricuit 41 causes the grid 43 to rise above cutofi initiating a flow of anode current in tube 45 simultaneously with the cutoff of anode current in tube 46. Voltage divider action of resistances 48, 49, and 56 together with variable resistive element 5| affords a means of applying required biasing voltages to tube 43 and 44 to obtain the desired operation of the trigger circuit 41 as described above.

voltage on grids 53 and 55. In order to produce anode current flow in tube 54, positive polarity signals must be simultaneously applied to the screengrid 53 and control grid 55.

Since tube 45 is normally nonconducting, a positive signal is normally applied to grid 33, since tube 24 is-normally conducting, a negative signal is normally applied to grid 55 and tube 54 will not conduct. Tube 54 will therefore conduct during such perids as tubes 24 and 45 are simultaneously nonconducting. c

In a similar manner anode51 of tube 46 is connected through impedance matching device 58 to the screen grid '59 of a second coincidence tube 66. The anode 38 of multivibrator 3 1.is connected to the control grid 6| of tube60. Simultaneous impression of positive polarity signals from anode 38 of multivibrator 31 and anode 51 of trigger circuit 41 is required to obtain an output from coincidence tube 68. Signals produced at the anodes of coincidence tube 54 and 60, respectively, are coupled through impedance matching devices 62 and 63 to conventional amplifiers 64 and 65. Low input capacitance of the cathode follower circuits employed as impedance matching devices 62, 63 improves the operation of pulse mixers 54, 60. Amplifiers 64 and 65 are preferably of similar construction thus simplifying adjustments thereof. Potentiometers 66, 61 in the anode circuits of amplifiers 64, 65 respectively serve as a means of equalizing the output signals from amplifiers 64, 65 for given signals applied thereto. Such an adjustment is necessary to minimize signal distortion in the output of the discrimination system |2.

Tubes .68 and 69, which may be any'conventional type power, amplifiers connected in pushpull, are driven from the outputs of amplifiers 64 and 65 respectively. The primary winding 16 of an output transformer 1|, connected across anode load resistances 12, and 13, providesvan integrating impedance network for the anode circuit. Signals applied to power amplifiers 68 and 69 are compared and an averaged output is obtained across secondary winding 14 or output trans former 1|. 7

In order that the operation of the specific embodiment shown in Fig. 2 may be more readily understood, it will now be described by way of example with reference to the waveforms shown in Fig. 3. v l

Repetitive multiple pulse signals emitted by transmitting device l6 and intercepted by receiving device comprise a pair of positive energy pulses having selectable pulse interval as mentioned hereinbefore. Typical ofthe energy received and applied to input terminals 20.for discrimination is waveform A of Fi 3. For purposes of illustration two multiple pulse signals are shown comprising a first pai of pulses and a second pair of pulses having a pulse interval less than that of the first pair of pulses. V Resulting pulses at the anode 22 are shown in waveform B. The first negative pulse coupled through capacitance 25 togrid .23 .of amplifier =24 causes anode current-cutoff in tube 24 land regenerative action of multivibrator 21 causes anode current flow 'in tube 25. Thus -a positive voltage excursion =a't anode 30 and a negative voltage excursion at .anode .39 results as indicated by numerals 1.5 of waveform C and lifiof waveform D respectively. The above conduction {state of multivibrator .2] .is maintained .until .the potential of gridQZS rises above cutoff, causing tubes 24, 25 to :return to the quiescent state condition as indicated by numer- .als Hand 18=of waveforms C and D respectively. The first pulse of thesecond pair of pulsesapplied Ito terminals 20 will resultin similar pulse .formation atanodes tll and 39 as indicated by numerals .19 ail 1.813 of-waveforms Cand D respectively.

Pulses from anode 3B of tube 24 are coupled through difierentiating network 3|, 32, 33 to the grid 34 of tube Action of the differentiating network .31., 32, 33 on the pulses shown in waveform C results .in the production of voltage pips coincidental with the leading and trailing edges of the .pulses .as shown by waveform E. In the quiescent state current flow in tube 35 of multivibrator 3.! is maintained as described hereinbefore, therefore the first negative pip indicated by numeral 8| in waveform E will interrupt current flow in tube 35. Thisnon-conductive condition of tube 3.5 will be maintained until the potential of .grid 34 rises above a definite voltage at which timeconduction conditions of multivibrator 3 as were existing during the quiescent state will be re-established. In accordance with the :above discussion positive pulses indicated by numerals 82., .8-3 in waveform F will be produced at anode 38. Regenerative switching action of multivibrator 31 results in the formation or negative pulses at anode 40 :as shown in waveform G coincidental with pulses :82, 8-3 of waveform F.

To prevent the interruption of anode current flow in tube 524 by the second pulse of a pair of pulses applied to input terminals 20, anode-4ll of tube 36 is coupled through a D.C.'-blockingicapacitance 84 to a second control grid 850i amplifier 2|. The potential "at anode 40 of tube 36 drops as shown by waveform Gefollowing the initiation oT-curr'enttfiowin tube .24. This drop in potential is conveyed to grid .85., rendering amplifier 2l non-responsive to signals applied thereto during an interval :of time after tube 24 has returned to a state of anode current conduction. Thus the second pulse indicated by numeral 85 of waveform A does not cause operation of multivibrator 21. Since pulse 86 is applied to amplifier 2| after tube 24 has returned to a quiescent condition, it does not appear in the output of amplifier 2| as shown in waveform B.

Pulses applied to terminals 29 are also applied to amplifier 4| as hereinbefore described. Negative pulses produced at anode 42 of amplifier 4| as shown in waveform H are coupled into grids 43 and. 44 of trigger circuit 4?. Since tube 45 is maintained non-conductive in the quiescent state,

negative pulses applied to grid 43 have no effect.

However, conduction by tube 46 will be cutoff by a negative pulse of sufiicient amplitude. Regenerative switching action raises grid 43 of tube 45 above cutoff thus initiating current flow therein. The above conditions initiated by the first one of a pair of pulses applied to trigger circuit 41 are maintained until a second negative pulse is applied thereto. The second negative pulse causes reverse switching action, thus interrupting conduction by anode 52 of tube 45 simultaneously with the initiation of conduction by tube 46. The

above described switching action resulting .from .the application of two successive negative pulses .totrigger circuit 441, produces a positive pulse at anode 51 of tube 46 and a coincidental negative pulse at anode 52 of tube 45 .as-shown in waveforms .I and J respectively, the duration of the pulses so formed being dependent upon the time interval between the pair of pulses applied to trigger .circuit 41..

To insure that anode current in :tube 45 is :cutoff prior to application of the first negative pulse to grid 43 .thereoi, the anode 38 of tube 35 is-connected through a difierentiating network, comprising capacitancedt'l and resistance -88 to asecand control grid 89 of tube 45. Positive pulses formed at anode 38 0f tube 3.5 asshown in waveform 1" are differentiated by capacitance 8 1 and resistance .88 to produce .a negative voltage excursionin time phase with the trailing edge-90:01" pulse 82. This negative voltage excursion applied to grid 89 of tube 45 causesanode currentcutoff therein resulting regenerative switching of trigger circuit 45!. If tube 45 is .in-the nonconducting quiescent state, the negative voltage excursion will :have no eflect thereon. Disturbance of the operation of the discrimination system by randon-noise isrthus minimized. I

As is apparent from waveform I. anode 54 of tube 46 is positive during the-interval between the leading edges of apulse pair. This voltageis applied to one grid 59 of coincidence-tube '60. Anode 38 of tube '35 is positive during the second of a pair-of equal periods. Thefirst period is initiated by the leading edge of-the first ,pulse, as shown in waveforms C and :D, and the second begins with the initiation of conduction in tube .86 in response to the end or the first period, as previously described and shown in waveforms F G. Since 't'l'iepositive voltage .1 from anode 8 applied to the other grid 61 of coincidence tube 60, it follows that when the second input pulse as pfith'e pair of pulses :s-hown in waveform .A occurs aft'er the initiation :of conduction initube the .high positive potential oi the grid 59 :and the grid fiil "will cause conduction by coincidence tube on in thetimeinterval between the initiation of conduction .by tube 3t and the arrival of the second pulse. This is indicated in waveform K which represents the voltage at the anode SJ-A. Similarly, anode 52 of tube 451s positive except during the interval between a pulse pair, as shown in waveform J. This voltage is applied to grid 53 of coincidence tube 54. Anode 30 of tube 24 is positive during the first of said pair of equal periods as shown in waveform C. This voltage is applied to the other grid 55 of coincidence tube 54. Therefore, whenever the second pulse of the pair of input pulses occurs before the initiation of conduction in tube 36, the high positive potential of the grid 53 and. the grid 55 will cause conduction by coincidence tube 54 in the time interval between the occurrence of the second pulse and the initiation of conduction by tube 36. This operation is shown in waveform L.

Upon recurrence of either of the above conductive conditions a recurrent voltage drop across the appropriate resistance 12 or 13 will cause impression of a signal of one polarity across primary winding Ill in amplitude dependency on the duration of each conductive period. Occurrence of the other conductive conduction at another instant in time will result in the impression of a signal of opposite polarity across primary winding 10.

In summation the discrimination system I! derives output signals having selectable amplitudes andpolarities dependent upon the pulse interval of repetitive pairs of pulses applied thereto.

From the foregoing discussion it is apparent that Considerable modification of the features of this invention is possible and while the device herein described and the form of apparatus for the operation thereof constitutes a preferred embodiment of the invention it is to be understood that the invention is not limited to this precise device and form of apparatus and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 7

What is claimed is:

1. In combination with a receiving device for the reception .of repetitive multiple pulse signal, a pulse discrimination system comprising; a pulse generator for deriving a pulse signal in response to input signals, a first gate pulse generator operable to produce a first gating signal upon reception of a first pulse signal, a second gate pulse generator responsive to the conclusion of the first gating signal to produce a second gating signal, a first coincidence circuit for producing a first output signal responsive to the attainment of selected time relationships between the operation of the pulse generator and the first gating pulse signal, a second coincidence circuit for producing a second output signal responsive to the attainment of selected time relationships between the operation of the pulse generator and the second gate pulse generator, and means combining the first and second output signal in amplitude opposition.

2. In combination with a receiving device for the reception of repetitive multiple pulse signals, a pulse discriminator system, comprising; a first trigger circuit having two stable conductivity states, coupling means producing trigger operation of the first trigger circuit in response to received pulse signals, a first gate generator operable to produce a first gating signal upon reception of a first pulse signal, a second gate pulse generator responsive to the conclusion of the first gating signal to produce a second gating siggame nal, a first coincidence circuit for producing a first output signal responsive to the attainment of selected time relationships between the operation of the pulse generator and the first gate pulse generator, a second coincidence circuit for producing a second output signal responsive to the attainment of selected time relationships between the operation of the pulse generator and the second gate pulse generator, and means combining the first and second output signal in amplitude opposition.

3. In combination with a receiving device for the reception of repetitive multiple pulse signals, a pulse discriminator system, comprising; a first trigger circuit having first and second stable conductivity states, coupling means producing trigger operation of the trigger circuit in response to received pulse signals, a second trigger circuit having one stable conductivity state and one unstable conductivity state, means initiating the unstable conductivity state therein in response to a first received pulse signal, a third trigger circuit having one stable conductivity state and one unstable conductivity state, means initiating the unstable state in the third trigger circuit in response to the return of the second trigger circuit to its stable state, first coincidence means responsive to simultaneous existence of the first state in the first trigger circuit and the unstable conductivity state in the second trigger circuit, second coincidence means responsive to simultaneous existence of the second state of the first trigger circuit and the unstable state in the third trigger circuit, and means combining the output signal from the first and second coincidence means in amplitude opposition.

GEORGE W. LENNY, J R. PAUL E. WARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,089,639 Bedford Aug. 10, 1937 2,359,447 Seeley Oct. 3, 1944 2,413,023 Young Dec. 24, 1946 2,416,088 Deerhake Feb. 18, 1947 2,416,306 Grieg Feb. 25, 1947 2,426,187 Earp Aug. 26, 1947 

